Tweet
The actual *BIG* (and this is the understatement of the century) difference between old and new transformers is that the old could be much more expensive (as in a Dual Showman cost as much as a car and a Fender FM212 costs like an not so expensive dinner for 2), so
1) could use the best materials that money could buy.
In *that* particular case, we are better off now, because thanks to technology advances,
a) we can have "better" wire (as in purer copper and thinner yet far more robust insulating epoxy enamel, instead of old oil based "synthetic enamel") and
b) better iron. (Metallurgy has advanced, we know better about alloys, heat treatment, microstructure, etc.)
2) could spend more on labor, meaning more time could be spent winding the transformer:
a) the winding could be very complex, lots of interlacing (this is about 10000 times more important than bobbin material, just "can't be seen from the outside"), alternating different wire sizes on alternate layers (cost prohibitive today), a winding could be spread into several interlaced sections , later connected in series, or even a single winding could be split in several same-turns smaller-wire-diameter ones connected in parallel (such as winding 4 x 0.5mm ones in parallel instead of a much harder 2mm one), etc.
2) they could wind at much lower RPM, letting the operator neatly place one wire perfectly besides the other.
These "mechanical" diferences are thousands of times more important than bobbin material.
Of course, if you take 2 to 4 hours to churn a transformer that an automated machine winds in 5 to 10 minutes, it will cost U$500 MSRP instead of U$80 to 150 and you might as well (commercially) shoot yourself in the head with a Magnum 44.
Another point: the difference in copper_inner_layer to core_iron distance caused by, say, a 1.5mm thick plastic bobbin instead of a 1mm thick paper core (minimum thickness, in fact I would *also* use at least 1.5 mm for mechanical reasons) is irrelevant.
If the bobbin is surrounded by a closed magnetic core (it is) , *all* magnetic lines of force (well, 99.9% of them) are guided (or pass through) by it.
Even if the magnetic material occupies only a part of the bobbin "hole".
Even if it's only 25% of its surface.
Usually real world transformers iron occupies 90/95% of that space, simply because laminations are not perfectly flat and have slightly rised edges or burrs to boot, subproduct of the punching process ... and this is true no matter what the bobbin is made of, of course.
As of:
yes, of course !! even I use them on my humble ones.
The cost is nil , in fact might even be cheaper than Pressphan (I guess that's your "fishpaper") because you can use a much thinner material.
Besides that it's *required* (at least insulating from primary to anything else) to pass HiPot tests certification (your UL and CSA certification or European CE and TÜV or strictest_in_the_world Scandinavian SEK norms).
Almost obsolete Pressphan (treated paper) is still used because many national or municipal norms for power line distribution transformers still require them to be insulated (and cooled) in an oil bath, and porous materials absorb oil, mylar does not.
In fact, a popular insulating material is a Pressphan+Mylar sandwich, where "the paper in oil satisfies the Politicians and the Mylar satisfies the Engineers".
Oh well.
So in my view, yes, there are quite appreciable differences in different output transformers, they can have easily audible effects, even to the extent of one being sweet sounding and another which externally looks as good or better being a piece of cr*p, but the cause of that is difficult or impossible to explain to the regular customer, so commercially it's much better to go the Mojo route.
1) could use the best materials that money could buy.
In *that* particular case, we are better off now, because thanks to technology advances,
a) we can have "better" wire (as in purer copper and thinner yet far more robust insulating epoxy enamel, instead of old oil based "synthetic enamel") and
b) better iron. (Metallurgy has advanced, we know better about alloys, heat treatment, microstructure, etc.)
2) could spend more on labor, meaning more time could be spent winding the transformer:
a) the winding could be very complex, lots of interlacing (this is about 10000 times more important than bobbin material, just "can't be seen from the outside"), alternating different wire sizes on alternate layers (cost prohibitive today), a winding could be spread into several interlaced sections , later connected in series, or even a single winding could be split in several same-turns smaller-wire-diameter ones connected in parallel (such as winding 4 x 0.5mm ones in parallel instead of a much harder 2mm one), etc.
2) they could wind at much lower RPM, letting the operator neatly place one wire perfectly besides the other.
These "mechanical" diferences are thousands of times more important than bobbin material.
Of course, if you take 2 to 4 hours to churn a transformer that an automated machine winds in 5 to 10 minutes, it will cost U$500 MSRP instead of U$80 to 150 and you might as well (commercially) shoot yourself in the head with a Magnum 44.
Another point: the difference in copper_inner_layer to core_iron distance caused by, say, a 1.5mm thick plastic bobbin instead of a 1mm thick paper core (minimum thickness, in fact I would *also* use at least 1.5 mm for mechanical reasons) is irrelevant.
If the bobbin is surrounded by a closed magnetic core (it is) , *all* magnetic lines of force (well, 99.9% of them) are guided (or pass through) by it.
Even if the magnetic material occupies only a part of the bobbin "hole".
Even if it's only 25% of its surface.
Usually real world transformers iron occupies 90/95% of that space, simply because laminations are not perfectly flat and have slightly rised edges or burrs to boot, subproduct of the punching process ... and this is true no matter what the bobbin is made of, of course.
As of:
, but are any transformers, custom or otherwise, made with Mylar film insulators?
The cost is nil , in fact might even be cheaper than Pressphan (I guess that's your "fishpaper") because you can use a much thinner material.
Besides that it's *required* (at least insulating from primary to anything else) to pass HiPot tests certification (your UL and CSA certification or European CE and TÜV or strictest_in_the_world Scandinavian SEK norms).
Almost obsolete Pressphan (treated paper) is still used because many national or municipal norms for power line distribution transformers still require them to be insulated (and cooled) in an oil bath, and porous materials absorb oil, mylar does not.
In fact, a popular insulating material is a Pressphan+Mylar sandwich, where "the paper in oil satisfies the Politicians and the Mylar satisfies the Engineers".
Oh well.
So in my view, yes, there are quite appreciable differences in different output transformers, they can have easily audible effects, even to the extent of one being sweet sounding and another which externally looks as good or better being a piece of cr*p, but the cause of that is difficult or impossible to explain to the regular customer, so commercially it's much better to go the Mojo route.
Comment